A pure inorganic aerogel photothermal evaporator and a preparation method thereof

Abstract

The application relates to the technical field of solar seawater desalination, and discloses a pure inorganic aerogel photothermal evaporator and a preparation method thereof. Clay, a boron source and a coupling agent are added into a chitosan solution to be stirred to obtain a precursor slurry; the precursor slurry is poured into a mold to be freeze-dried to obtain a base precursor; the base precursor is heated at high temperature to obtain a clay base layer; a metal M salt and / or a metal M salt hydrate, sodium thiosulfate and / or sodium thiosulfate hydrate and clay are dispersed into water, and acid is added to adjust the pH to be acidic; after stirring, filtering, washing and drying, the clay photothermal agent with metal sulfide grown on the surface is obtained; the clay photothermal agent is dispersed into an ethyl silicate hydrolysis solution, is coated on the surface of the clay base layer, and is dried to obtain the aerogel photothermal evaporator. The high-strength and high-stability pure inorganic clay aerogel photothermal evaporator obtained by the application has corrosion resistance and can be used for solar seawater desalination under complex environments and harsh conditions.

Description

Technical Field

[0001] This invention relates to the field of solar seawater desalination technology, and in particular to a pure inorganic aerogel photothermal evaporator and its preparation method. Background Technology

[0002] Freshwater shortages are becoming increasingly severe due to climate change and rapid population growth. Among existing freshwater production methods, solar-powered interfacial evaporation is considered promising and efficient. Compared to reverse osmosis and multi-effect distillation, it uses sunlight directly as an energy source, avoiding the consumption of fossil fuels and electricity. Furthermore, since the photothermal conversion occurs only at the interface, heat loss in the bulk water is reduced. To achieve stable and efficient steam generation, solar-powered interfacial evaporators need to possess the following characteristics: efficient sunlight-steam conversion, rapid water transport, and resistance to salt accumulation. Simultaneously, low cost, sustainability, and processing flexibility are also important principles in evaporator design.

[0003] Based on the above principles, aerogel materials with high porosity are beneficial for mass transport and thermal insulation, making them an ideal choice for photothermal evaporators. Existing aerogel evaporators primarily focus on improving the light absorption rate, hydrophilicity, resistance to salt accumulation, and evaporation rate of the materials. For example, hydroxyl-rich polymers such as polyvinyl alcohol, chitosan, and sodium alginate are often used to construct the hydrophilic framework. Pyrrole, dopamine, and tannic acid are often used for surface modification to enhance light absorption. Furthermore, to adapt to real-world complex environments, aerogel evaporators must also possess high strength, corrosion resistance, and stability. Therefore, many inorganic carbon materials are used in the construction of aerogel evaporators, such as graphene and carbon nanotubes. However, the high cost of these raw materials limits the practicality of aerogel evaporators. In recent years, low-cost and sustainable clay-based aerogels have become popular candidates for photothermal evaporators, such as montmorillonite / starch aerogel (Desalination, 2022, 541, 116028), attapulgite / polyvinyl alcohol aerogel (Separation and Purification Technology, 2021, 271, 118869), and hydroxyapatite / chitosan aerogel (Advanced Functional Materials, 2022, 32(9), 2106978).

[0004] However, clay itself is difficult to form a high-strength, lightweight framework, and a large amount of polymer components still need to be added to improve its mechanical properties, which contradicts the design philosophy of inorganic materials. Therefore, clay aerogels with purely inorganic components still require reasonable structural design.

[0005] Therefore, there is an urgent need for a pure inorganic aerogel photothermal evaporator and its preparation method to solve the above-mentioned technical problems. Summary of the Invention

[0006] The purpose of this invention is to manufacture a high-strength and corrosion-resistant pure inorganic aerogel photothermal evaporator. A boron source is introduced into a clay aerogel precursor, which is then calcined at high temperature to form a high-strength clay substrate layer. Subsequently, a clay photothermal agent with metal sulfides grown on the surface is coated as a photothermal layer, thereby realizing the construction of a pure inorganic clay aerogel photothermal evaporator that combines high strength and corrosion resistance.

[0007] To achieve the above objectives, the present invention is implemented according to the following technical solution:

[0008] A pure inorganic aerogel photothermal evaporator, comprising a clay substrate layer and a clay photothermal layer coated on the surface of the clay substrate layer.

[0009] Specifically, the clay base layer is obtained by adding clay, boron source, and coupling agent to a chitosan solution, stirring until homogeneous, and then freeze-drying and heating at high temperature to remove organic matter. The clay photothermal layer is a thin layer formed by dispersing clay photothermal agent in tetraethyl orthosilicate hydrolysate, coating and drying.

[0010] A method for preparing a pure inorganic aerogel photothermal evaporator includes the following steps:

[0011] S1, Preparation of precursor slurry:

[0012] Clay, boron source, and coupling agent were added to the chitosan solution and stirred to obtain a uniformly mixed precursor slurry.

[0013] S2, Preparation of clay base layer:

[0014] After pouring the precursor slurry into a mold, freeze-dry it to obtain the substrate precursor. After heating the substrate precursor at high temperature, a clay substrate layer is obtained.

[0015] S3, Preparation of clay photothermal agent:

[0016] Metal M salt and / or metal M salt hydrate, sodium thiosulfate and / or sodium thiosulfate hydrate, and clay are dispersed in water, and the pH is adjusted to acidic by adding acid; after stirring, filtering, washing, and drying, a clay photothermal agent for surface growth of metal sulfides is obtained.

[0017] S4, Preparation of an aerogel photothermal evaporator:

[0018] The clay photothermal agent is dispersed in tetraethyl orthosilicate hydrolysate, then coated onto the upper surface of a clay substrate, and dried to form a clay photothermal layer, thus obtaining an aerogel photothermal evaporator. Preferably, in step S1, the coupling agent is a silane coupling agent; specifically, the silane coupling agent is KH560.

[0019] Preferably, in step S1, the clay is one of halloysite (HNT), kaolinite (KLT), montmorillonite (MMT), and attapulgite (APT).

[0020] Preferably, in step S1, the boron source is either boric acid (H3BO3) or borax (4H3BO3·Na2O·4H2O).

[0021] Preferably, in step S1, the boron source is denoted as H3BO3, and the mass ratio of clay, boron source, and coupling agent is 100:(75-100):(75-100).

[0022] Preferably, in step S1, the chitosan solution is obtained by mixing chitosan, glacial acetic acid, and water; the mass fraction of chitosan in the chitosan solution is 2-5 wt%; the mass-volume ratio of chitosan to glacial acetic acid is 12.5:3.5, and the unit of mass-volume ratio is g:mL.

[0023] Preferably, in step S1, the boron source is denoted as H3BO3, and the mass-to-volume ratio of the sum of the masses of clay, boron source, coupling agent, and chitosan to the precursor slurry is 25-50:100, with the unit of mass-to-volume ratio being g:mL.

[0024] Preferably, in step S2, the high-temperature heating temperature is 800-1000℃; the high-temperature heating time is 4 hours.

[0025] Preferably, in step S3, M is one of the metallic elements Cu, Mo, Fe, Ag, Co, and Ni.

[0026] Preferably, in step S3, the metal M salt hydrate is calculated as metal M salt, the sodium thiosulfate hydrate is calculated as sodium thiosulfate, and the ratio of clay, metal M salt and / or metal M salt hydrate, sodium thiosulfate and / or sodium thiosulfate hydrate is 100∶(1-2.5)∶(1-5), with the comparison unit being g∶mol∶mol.

[0027] Preferably, in step S3, the acid used to adjust the pH is one of glacial acetic acid, oxalic acid, or citric acid.

[0028] Preferably, in step S4, the volume ratio of tetraethyl orthosilicate to water in the tetraethyl orthosilicate hydrolysate is (2-5):(95-98); the mass-volume ratio of clay photothermal agent to tetraethyl orthosilicate hydrolysate is 1:10 based on the mass of clay, and the comparison unit is g:mL.

[0029] Specifically, the tetraethyl orthosilicate hydrolysate is a mixed solution of tetraethyl orthosilicate and water, and a 12 mol / L solution is added during its preparation. -1 Hydrochloric acid is used as a catalyst (the amount of hydrochloric acid used in the preparation of tetraethyl orthosilicate hydrolysate is small and does not participate in the calculation of the volume concentration of tetraethyl orthosilicate hydrolysate), and the volume ratio of hydrochloric acid used to the volume of the mixed solution (the volume of the mixed solution here is the sum of the volumes of tetraethyl orthosilicate and water in the tetraethyl orthosilicate hydrolysate) is 0.1 mL : 100 mL.

[0030] Preferably, the clay photothermal agent is uniformly coated on the upper surface of the clay substrate layer; the coverage amount of the clay photothermal agent on the upper surface of the clay substrate layer, based on the mass of clay in the clay photothermal agent, is 0.05-0.1 g cm³. -3 The coverage here is calculated based on the mass of clay photothermal agent per square centimeter covering the upper surface of the clay base layer (for ease of calculation, the clay photothermal agent is calculated based on the mass of clay contained in it).

[0031] Specifically, step S1 includes the following steps:

[0032] Clay, a boron source (denoted as H3BO3), and a coupling agent (specifically KH560) were added to a chitosan solution at a mass ratio of 100:(75-100):(75-100). The mixture was stirred at 30°C for 8 hours to obtain a uniformly mixed precursor slurry. The chitosan solution was obtained by mixing chitosan and acetic acid in water in a fixed proportion, with 3.5 mL of glacial acetic acid added for every 12.5 g of chitosan, wherein the mass fraction of chitosan was 2-5 wt%. The total content of clay, boron source (denoted as H3BO3), coupling agent, and chitosan in the slurry was 25-50 g per 100 mL.

[0033] Specifically, step S2 includes the following steps:

[0034] After pouring the precursor slurry into a mold, it is freeze-dried to obtain the substrate precursor. The substrate precursor is then heated in a muffle furnace at a high temperature of 800-1000℃ to obtain the substrate layer. When the clay is halloysite (HNT), kaolinite (KLT), montmorillonite (MMT), or attapulgite (APT), the corresponding substrate precursors obtained following steps S1 and S2 are denoted as raw-HBK, raw-KBK, raw-MBK, and raw-ABK, respectively. The corresponding substrate layers obtained after calcination (i.e., the high-temperature heating process) are denoted as HBK, KBK, MBK, and ABK, respectively.

[0035] Specifically, step S3 includes the following steps:

[0036] Clay, metal M salt and / or metal M salt hydrate (calculated as metal M salt), sodium thiosulfate and / or sodium thiosulfate hydrate (calculated as sodium thiosulfate) are mixed in a ratio of 100:(1-2.5):(1-5) (the comparison unit is g:mol:mol), and the pH is adjusted to acid. The mixture is stirred at 90°C for 12 hours, filtered, washed, and dried to obtain a clay photothermal agent for surface growth of metal sulfides.

[0037] The clay used is halloysite (HNT), kaolinite (KLT), montmorillonite (MMT), and attapulgite (APT); the corresponding clay photothermal agents obtained according to step S3 above are denoted as MS. x @HNT、MS x @KLT、MS x @MMT、MS x @APT.

[0038] Specifically, step S4 includes the following steps:

[0039] clay photothermal agent MS x @HNT、MS x @KLT、MS x @MMT、MS x @APT was dispersed in tetraethyl orthosilicate hydrolysate, then coated onto the upper surface of corresponding HBK, KBK, MBK, and ABK clay substrates. After drying, a clay photothermal layer was formed, resulting in an aerogel photothermal evaporator, denoted as MS. x @HNT / HBK、MS x @KLT / KBK、MS x @MMT / MBK、MS x @APT / ABK.

[0040] The clay photothermal agent is the same clay used in the clay base layer.

[0041] Preparation method of tetraethyl orthosilicate hydrolysate: Mix 2-5 mL of tetraethyl orthosilicate with 0.01 mL of 12 mol / L hydrolysate. -1 Hydrochloric acid was added to 95-98 mL of water (where the total volume of tetraethyl orthosilicate and water was 100 mL), and the mixture was stirred at room temperature until the solution became clear and transparent, yielding a 2-5 vol% tetraethyl orthosilicate hydrolysate. The ratio of clay photothermal agent (based on clay mass) to tetraethyl orthosilicate hydrolysate was 1 g: 10 mL.

[0042] The pure inorganic clay aerogel photothermal evaporator obtained by this invention can be used for solar seawater desalination and has the characteristics of high strength, corrosion resistance, high photothermal efficiency, good purification effect and long-term stability.

[0043] Mechanism of action:

[0044] Aerogel is a porous material characterized by low density and high porosity. Seawater can be transported from the bottom of the aerogel evaporator to the surface through capillary action. The photothermal layer on the aerogel surface absorbs sunlight and converts it into heat energy. The water on the aerogel surface evaporates under heat, and the high-concentration brine on the surface diffuses back to the bottom.

[0045] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0046] This invention provides a high-strength, corrosion-resistant, and highly stable pure inorganic clay aerogel photothermal evaporator. The high-strength aerogel substrate obtained through high-temperature calcination is coated with metal sulfides grown on the clay surface as a photothermal agent, forming a photothermal layer with high photothermal efficiency. The pure inorganic material also makes the aerogel evaporator corrosion-resistant, allowing it to be used in solar-powered seawater desalination under complex and harsh conditions. Attached Figure Description

[0047] Figure 1 Here is a SEM image of the clay photothermal agent CuS@HNT from Example 1;

[0048] Figure 2 XRD analysis of the clay photothermal agent CuS@HNT in Example 1;

[0049] Figure 3 The light absorption rates of the clay photothermal agent CuS@HNT in Example 1, the photothermal agent CuS in Comparative Example 2, the photothermal agent CuSHNT mix in Comparative Example 3, and halloysite (HNT) were tested.

[0050] Figure 4 Water contact angle tests were conducted on the clay photothermal agent CuS@HNT of Example 1 and the photothermal agent CuS of Comparative Example 2.

[0051] Figure 5 Here are SEM images of the cross-section and longitudinal section of the clay substrate HBK in Example 1;

[0052] Figure 6 The images show SEM images of the wall surfaces of the raw-HBK substrate precursor and the clay substrate HBK in Example 1.

[0053] Figure 7 XRD analysis of the clay substrate HBK in Example 1;

[0054] Figure 8Thermogravimetric analysis of the clay base layer HBK in Example 1;

[0055] Figure 9 Compression stress analysis of the clay base layer HBK in Example 1;

[0056] Figure 10 The aerogel evaporator CuS@HNT / HBK of Example 1, the aerogel evaporator HBK of Comparative Example 1, and the aerogel evaporator CuS / HBK of Comparative Example 2 under sunlight (1000W m) -2 Evaporation rate and efficiency;

[0057] Figure 11 The evaporation rates of the CuS@MMT / MBK aerogel evaporator in Example 2 under different light intensities;

[0058] Figure 12 The evaporation rates of the aerogel evaporator MoS2@HNT / HBK in Example 3 at different brine concentrations;

[0059] Figure 13 The resistance values ​​of the CuS@HNT / HBK(Na) aerogel evaporator in Example 4 before and after evaporation of brine of different concentrations are shown.

[0060] Figure 14 The pH values ​​of the CuS@HNT / HBK (2wt%) aerogel evaporator in Example 5 before and after evaporation of acid and alkaline solutions;

[0061] Figure 15 Evaporation cycle test of CuS@HNT / HBK (Acetic acid) aerogel evaporator in Example 6;

[0062] Figure 16 Salt accumulation resistance test of CuS@HNT / HBK (1000°C) aerogel evaporator of Example 7. Detailed Implementation

[0063] The present invention will be further described below with reference to specific embodiments. The illustrative embodiments and descriptions herein are used to explain the present invention, but are not intended to limit the present invention.

[0064] There are no particular restrictions on the source of any raw materials used in this invention; they can be purchased from the market or prepared using conventional methods known to those skilled in the art.

[0065] There are no particular restrictions on the purity of any of the raw materials used in this invention; however, it is preferred to use materials with conventional purity levels used in the field.

[0066] The apparatus used in this invention, unless otherwise specified, is a commonly used apparatus in the field, whose operation and usage are well known to those skilled in the art.

[0067] Except for Example 5, the chitosan solution in the following examples was obtained by mixing chitosan and glacial acetic acid in water, with 3.5 mL of glacial acetic acid added for every 12.5 g of chitosan, wherein the mass fraction of chitosan was 5 wt%.

[0068] In Example 5, the chitosan solution was obtained by mixing chitosan and glacial acetic acid in water, with 3.5 mL of glacial acetic acid added for every 12.5 g of chitosan, wherein the mass fraction of chitosan was 2 wt%.

[0069] In the following examples, the 5 vol% tetraethyl orthosilicate hydrolysate was prepared as follows: 5 mL of tetraethyl orthosilicate and 0.01 mL of 12 mol / L tetraethyl orthosilicate hydrolysate were added. -1 Hydrochloric acid was added to 95 mL of water and stirred at room temperature until the solution became clear and transparent, yielding a 5 vol% tetraethyl orthosilicate hydrolysate.

[0070] In the following examples, the halloysite used has the chemical formula Al2O3·2SiO2·4H2O, and the montmorillonite used has the chemical formula Al2O3·4SiO2·H2O.

[0071] Example 1

[0072] A method for preparing a pure inorganic clay aerogel photothermal evaporator includes the following steps:

[0073] S1, Preparation of precursor slurry:

[0074] 8g halloysite, 6g boric acid, and 6g KH560 were uniformly dispersed in 50mL of 5wt% chitosan solution and stirred at 30℃ for 8h to obtain a uniformly mixed precursor slurry.

[0075] S2, Preparation of clay base layer:

[0076] After the precursor slurry is poured into a mold, it is freeze-dried to obtain the substrate precursor, denoted as raw-HBK. The substrate precursor is placed in a muffle furnace and heated at 800℃ for 4 hours to obtain the clay substrate layer, denoted as HBK.

[0077] S3, Preparation of clay photothermal agent: 1g halloysite, 2.6g copper sulfate pentahydrate, and 2.6g sodium thiosulfate pentahydrate were dispersed in 100mL of water, and the pH was adjusted to acidic with citric acid. The mixture was stirred at 90℃ for 12h, filtered, washed, and dried to obtain a clay photothermal agent with copper sulfide growing on its surface, denoted as CuS@HNT.

[0078] S4, Preparation of an aerogel photothermal evaporator:

[0079] Clay photothermal agent (CuS@HNT) was dispersed in 10 mL of 5 vol% tetraethyl orthosilicate hydrolysate, and then coated onto the upper surface of the clay substrate (HBK) (the upper surface is a circle with a diameter of 4 cm). After drying, a clay photothermal layer was formed, and then an aerogel photothermal evaporator was obtained, denoted as CuS@HNT / HBK.

[0080] The clay photothermal agent obtained in step S3 is applied to the upper surface of the clay substrate.

[0081] Performance testing:

[0082] Evaporation rate test: CuS@HNT / HBK was placed in a container containing the solution to be tested. The mass change of the container was measured using an electronic balance. The evaporation rate was tested under different light conditions. The evaporation rate is the mass change of the evaporator per unit area per unit time (kg m²). 2 h -1 The solutions to be tested included: seawater, NaCl solutions of different concentrations, acidic water, alkaline water, and dyed water. Lighting conditions included: outdoor sunlight and indoor xenon lamp light.

[0083] Water quality testing: A condensate collector with a transparent cover was added to the outside of the container. The evaporated water vapor condensed into water droplets on the transparent cover and fell back into the condensate collector below. The resistance value of the collected condensate was tested with a multimeter, the pH value was tested with a pH meter, and the absorbance value was tested with a UV-Vis spectrophotometer.

[0084] Example 2

[0085] In this embodiment, the clay was replaced with montmorillonite (MMT), and the remaining steps and performance tests were the same as in Example 1. The obtained clay substrate was denoted as MBK, the obtained clay photothermal agent was denoted as CuS@MMT, and the obtained aerogel photothermal evaporator was denoted as CuS@MMT / MBK.

[0086] Example 3

[0087] In this embodiment, the metal M salt was replaced with sodium molybdate (Na2MoO4) at a dosage of 2.06 g, and sodium thiosulfate pentahydrate at a dosage of 4.12 g. The remaining steps and performance tests were the same as in Example 1. The resulting clay substrate was designated HBK, the resulting clay photothermal agent was designated MoS2@HNT, and the resulting aerogel photothermal evaporator was designated MoS2@HNT / HBK.

[0088] Example 4

[0089] In this embodiment, the boron source was replaced with borax (4H3BO3·Na2O·4H2O), with a dosage of 9.26g. The remaining steps and performance tests were the same as in Example 1. The obtained clay substrate layer was denoted as HBK(Na), the obtained clay photothermal agent was denoted as CuS@HNT, and the obtained aerogel photothermal evaporator was denoted as CuS@HNT / HBK(Na).

[0090] Example 5

[0091] In this embodiment, the chitosan concentration was changed to 2 wt%, and the remaining steps and performance tests were the same as in Example 1. The obtained clay substrate layer was denoted as HBK (2 wt%), the obtained clay photothermal agent was denoted as CuS@HNT, and the obtained aerogel photothermal evaporator was denoted as CuS@HNT / HBK (2 wt%).

[0092] Example 6

[0093] In this embodiment, glacial acetic acid was used to adjust the pH value, and the remaining steps and performance tests were the same as in Example 1. The obtained clay substrate layer was denoted as HBK, the obtained clay photothermal agent was denoted as CuS@HNT(Acetic acid), and the obtained aerogel photothermal evaporator was denoted as CuS@HNT / HBK(Acetic acid).

[0094] Example 7

[0095] In this embodiment, the high-temperature calcination temperature was 1000℃, and the remaining steps and performance tests were the same as in Example 1. The obtained clay base layer was denoted as HBK(1000℃), the obtained clay photothermal agent was denoted as CuS@HNT, and the obtained aerogel photothermal evaporator was denoted as CuS@HNT / HBK(1000℃).

[0096] Comparative Example 1

[0097] This comparative example uses only the clay substrate layer used in Example 1. The resulting substrate layer is denoted as HBK, and the aerogel photothermal evaporator is denoted as HBK.

[0098] Comparative Example 2

[0099] In this comparative example, halloysite was not added during the synthesis of the photothermal agent, and all other steps and performance tests were the same as in Example 1. The resulting substrate was denoted as HBK, the photothermal agent as CuS, and the aerogel photothermal evaporator as CuS / HBK.

[0100] Comparative Example 3

[0101] In this comparative example, halloysite was mechanically mixed 1:1 with the CuS photothermal agent synthesized in Comparative Example 2 as the photothermal agent. All other steps and performance tests were the same as in Example 1. The resulting substrate was denoted as HBK, the photothermal agent as CuS HNT mix, and the aerogel photothermal evaporator as CuS HNT mix / HBK.

[0102] like Figure 1 The image shown is a SEM image of the clay photothermal agent CuS@HNT from Example 1. It can be seen that CuS particles grow uniformly on the HNT surface, forming a rod-shaped structure with a high aspect ratio.

[0103] like Figure 2 As shown, the XRD analysis of the clay photothermal agent CuS@HNT in Example 1 shows that CuS@HNT exhibits both strong CuS characteristic peaks (corresponding to PDF#06-0464) and relatively weak halloysite characteristic peaks (corresponding to PDF#09-0453), and there is no significant shift compared to the characteristic peaks of pure halloysite. This indicates that CuS was successfully synthesized and the structure of halloysite did not change.

[0104] like Figure 3 The image shows the light absorption rate tests of the clay photothermal agent CuS@HNT in Example 1, the photothermal agent CuS in Comparative Example 2, the photothermal agent CuS HNT mix in Comparative Example 3, and halloysite (HNT). Figure 3 Figure a shows the absorption rate curve. Figure 3 Figure b shows the average absorbance. As can be seen from the figure, the absorbance of pure CuS (93.0%) is significantly higher than that of pure HNT (32.6%), while the absorbance of the CuS@HNT mix (85.6%) falls between the two. Notably, the absorbance of CuS@HNT (98.3%) is significantly different from that of the equal-proportion mechanical mixture, and even higher than that of pure CuS. The high absorbance of CuS@HNT is beneficial for the absorption and utilization of sunlight.

[0105] like Figure 4 The image shows the water contact angle test results for the clay photothermal agent CuS@HNT in Example 1 and the photothermal agent CuS in Comparative Example 2. Figure 4 Figure a shows the wetting process of the clay photothermal agent CuS@HNT in Example 1. Figure 4 Figure b shows the wetting process of CuS, the photothermal agent in Comparative Example 2. Although both exhibit hydrophilicity, there is a significant difference in the time it takes for water droplets to completely diffuse on the material surface. Water diffuses completely on the CuS@HNT surface in only 0.2 s, while it takes 7 s to diffuse completely on the CuS surface. This is because the halloysite surface has abundant hydroxyl groups, which enhances the hydrophilicity of CuS@HNT.

[0106] like Figure 5The image shows cross-sectional and longitudinal SEM images of the clay substrate HBK in Example 1. It can be seen that it exhibits vertical channels in the longitudinal direction and a layered porous structure in the transverse direction. This porous structure facilitates rapid water transport.

[0107] like Figure 6 The image shows SEM images of the walls of the aerogel precursor raw-HBK and the clay substrate HBK in Example 1. Halloysite is clearly visible on the walls of the aerogel precursor, while the walls of the substrate formed by high-temperature calcination have melted.

[0108] like Figure 7 The image shows the XRD analysis of the clay substrate HBK in Example 1. HBK exhibits strong diffraction peaks for aluminum borate (corresponding to PDF#53-1233) and relatively weak diffraction peaks for silica (corresponding to PDF#12-0708), while the diffraction peaks for the raw material halloysite completely disappear. This indicates that at high temperatures, boric acid and alumina in halloysite react to form aluminum borate, while silica in halloysite remains.

[0109] like Figure 8 The image shows the thermogravimetric analysis of the clay substrate HBK in Example 1. The high-temperature pyrolysis of the substrate precursor raw-HBK to HBK has four main stages: the weight loss from 100°C to 120°C is the evaporation of adsorbed water in the material; the weight loss around 150°C to 170°C is the dehydration of silicic acid to form amorphous silica and the dehydration of boric acid to form metaboric acid; the stage from 250°C to 400°C is the high-temperature oxidative decomposition of organic matter; and after 425°C is the dehydroxylation process of halloysite, at which point the Al-O bonds in halloysite are exposed and react with metaboric acid to form aluminum borate.

[0110] like Figure 9 The figure shows the compressive stress analysis of the substrate precursor raw-HBK and the clay substrate HBK in Example 1. After the substrate precursor raw-HBK was pyrolyzed to generate HBK, the compressive strength increased from 3.47 MPa to 4.80 MPa, and the compressive modulus increased significantly from 9.9 MPa to 31.7 MPa.

[0111] like Figure 10 As shown, the aerogel evaporator CuS@HNT / HBK of Example 1, the aerogel evaporator HBK of Comparative Example 1, and the aerogel evaporator CuS / HBK of Comparative Example 2 are shown under sunlight (1000W m²). -2 The evaporation rate and efficiency of HBK are shown. It can be seen that the evaporation rate of HBK is 0.70 kg / m³. -2 h -1 The evaporation rate of CuS / HBK is 1.39 kg m³. -2 h -1The evaporation rate of CuS@HNT / HBK is 1.52 kg m³. -2 h -1 Due to the absence of a photothermal conversion layer, the evaporation rate of HBK is significantly lower than that of CuS / HBK and CuS@HNT / HBK. Furthermore, since CuS has lower absorbance and water wetting rate than CuS@HNT / HBK, the evaporation rate of CuS / HBK is also lower than that of CuS@HNT / HBK.

[0112] like Figure 11 The figure shows the evaporation rate of the CuS@MMT / MBK aerogel evaporator in Example 2 under different light intensities. The evaporation rate of CuS@MMT / MBK increases with increasing light intensity, because the surface temperature of CuS@MMT / MBK is higher under higher light intensities, which promotes water evaporation.

[0113] like Figure 12 The figure shows the evaporation rate of the aerogel evaporator MoS2@HNT / HBK in Example 3 at different brine concentrations. The evaporation rate of MoS2@HNT / HBK decreases with increasing salt concentration, and the decrease is greater at lower concentrations than at higher concentrations.

[0114] like Figure 13 The figure shows the resistance values ​​of the CuS@HNT / HBK(Na) aerogel evaporator in Example 4 before and after evaporation of brine of different concentrations. The resistance values ​​of the condensate obtained from brine of different concentrations all increased significantly and were similar to those of pure water, indicating that CuS@HNT / HBK(Na) has a good water purification effect.

[0115] like Figure 14 The figure shows the pH values ​​of the CuS@HNT / HBK (2wt%) aerogel evaporator in Example 5 before and after evaporation of acid and alkaline solutions. The pH values ​​of the condensate from different sources are all close to 7, indicating that CuS@HNT / HBK (2wt%) has a good water purification effect.

[0116] like Figure 15 The image shows the evaporation cycle test of the CuS@HNT / HBK (Acetic acid) aerogel evaporator in Example 6. Ten cycles demonstrate that the evaporation rate can remain stable over a long period.

[0117] like Figure 16The image shows the salt accumulation resistance test of the CuS@HNT / HBK (1000℃) aerogel evaporator of Example 7. 0.25g of NaCl crystals were placed on the surface of CuS@HNT / HBK (1000℃). The NaCl crystals were wetted by water and gradually dissolved, disappearing completely after 1 hour. This indicates that CuS@HNT / HBK (1000℃) resists salt accumulation through surface wetting.

[0118] The technical solutions of the present invention are not limited to the specific embodiments described above. Any technical modifications made in accordance with the technical solutions of the present invention fall within the protection scope of the present invention.

Claims

1. A method for preparing a pure inorganic aerogel photothermal evaporator, characterized by: The pure inorganic aerogel photothermal evaporator comprises a clay substrate layer and a clay photothermal layer on the upper surface of the clay substrate layer; The preparation method comprises the following steps: S1, preparing a precursor slurry: The clay, boron source and coupling agent are added into the chitosan solution and stirred to obtain a uniformly mixed precursor slurry; S2, preparing a clay substrate layer: The precursor slurry is poured into a mold and freeze-dried to obtain a substrate precursor, and the substrate precursor is heated at high temperature to obtain the clay substrate layer; S3, preparing a clay photothermal agent: The metal M salt and / or metal M salt hydrate, sodium thiosulfate and / or sodium thiosulfate hydrate and clay are dispersed in water, and the pH is adjusted to be acidic by adding acid; after stirring, filtering, washing and drying, the clay photothermal agent with metal sulfide grown on the surface is obtained; S4, preparing an aerogel photothermal evaporator: The clay photothermal agent is dispersed in a tetraethyl orthosilicate hydrolysate, and then coated on the upper surface of the clay substrate layer, and after drying, a clay photothermal layer is formed, and then the aerogel photothermal evaporator is obtained; In the step S1, the clay is one of halloysite, kaolin, montmorillonite and attapulgite; In the step S1, the boron source is one of boric acid and borax; In the step S3, M is one of metal elements Cu, Mo, Fe, Ag, Co and Ni; The clay photothermal agent is the same as the clay used in the clay substrate layer.

2. The method of claim 1, wherein the method is characterized by: In the step S1, the boron source is denoted as H3BO3, and the mass ratio of the clay, the boron source and the coupling agent is 100:(75-100):(75-100).

3. The method of claim 1, wherein the method further comprises: In the step S1, the chitosan solution is obtained by mixing chitosan, glacial acetic acid and water; the mass fraction of chitosan in the chitosan solution is 2-5wt%; and the mass-volume ratio of chitosan to glacial acetic acid is 12.5:3.5, wherein the unit of the mass-volume ratio is g:mL.

4. The method of claim 1, wherein the method further comprises: In the step S1, the boron source is denoted as H3BO3, and the mass-volume ratio of the sum of the mass of the clay, the boron source, the coupling agent and chitosan to the precursor slurry is 25-50:100, wherein the unit of the mass-volume ratio is g:mL.

5. The method of claim 1, wherein the method further comprises: In the step S2, the temperature of high-temperature heating is 800-1000°C; and the time of high-temperature heating is 4 h.

6. The method of claim 1, wherein: In the step S3, the metal M salt hydrate is calculated based on the metal M salt, the sodium thiosulfate hydrate is calculated based on the sodium thiosulfate, and the ratio of the clay, the metal M salt and / or metal M salt hydrate, the sodium thiosulfate and / or sodium thiosulfate hydrate is 100:(1-2.5):(1-5), wherein the unit of the ratio is g: mol: mol; In the step S4, in the tetraethyl orthosilicate hydrolysate, the volume ratio of tetraethyl orthosilicate to water is (2-5):(95-98); and the mass-volume ratio of the clay photothermal agent to the tetraethyl orthosilicate hydrolysate is 1:10, wherein the unit of the mass-volume ratio is g:mL.

Images